The present invention relates to locking systems, and, more particularly, to electronic locking systems which are actuated by inputting a correct code.
The use of electronic combination locks is well known. More specifically, such combination locks usually employ a plurality of switches which, when set to correspond to a predetermined code, are used to actuate a solenoid or similar device to unlock a door. Alternately, the electronic combination lock may be triggered by opening and closing a single switch in a timed predetermined sequence.
The following patents relate to this general area:
______________________________________ Patent No. Issue Date ______________________________________ 3,660,729 - James et al May 2, 1972 3,710,316 - Kromer Jan. 9, 1973 3,751,718 - Hanchett, Jr. Aug. 7, 1973 4,093,870 - Epstein June 6, 1978 ______________________________________
The James et al patent discloses an electronic combination lock for unlocking a locking bar used on an enclosure. The system includes a decoder having a built-in combination based on correct number, sequence, and spacing of digits input into the circuit.
The Kromer patent discloses a vehicle electrical combination lock including a series of switches which are used to input a sequential code.
The Hanchett patent discloses an electronic car door unlocking circuit including a single pair of electrical contacts which are sequentially operated to input a code. A cycle counter, display, memory register, code select switches and gates are used in the circuit. A timing light is used such that the person operating the lock switch may be aware of the timing intervals. The contacts may be those of a push button switch located below the car door handle.
The Epstein patent discloses circuitry for use as either a reflex tester or a combination lock wherein a single switch is used for turning on the circuitry and for inputting coded signals. A light is used to indicate the timing intervals to the person using the apparatus.
Although the above and other prior art devices have been somewhat useful in providing electronic combination locks, they have usually been subject to one or more of several disadvantages.
One of these disadvantages is that such prior art devices are usually visible to a potential intruder. That is, someone approaching a door protected by such combination locks will usually see the switch or switches and thereby deduce the existence of the electronic combination lock. This may aid the intruder in attempting to neutralize or overcome the electronic lock.
A further disadvantage of many of these prior art devices is that they require the drilling of holes or otherwise time consuming modifications to the pre-existing enclosure in order to mount the electronic combination lock.
Yet another disadvantage common to the prior art is that such devices unnecessarily use power when no one is operating them. That is, their quiescent power consumption is higher than necessary. Further, such electronic combination circuits function even when the door is unlocked. This results in an even greater waste of energy.